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Topic Review (Newest First)

11-14-2005, 02:58 AM

Brett Anderson

Re: Dreaming of Dragons

GM.

With more power, why do you need a shorter ratio?

Most of our forced induction customers go to a taller ratio for traction reasons. Once you're moving (with a bunch of HP), traction doesn't matter so much.

I do hope that I'll be the one converting my 3.64 Quaife to 3.91 for you. I know I can do it less than Dinan will, and better yet, I'll do it the right way. Email me privately for how Dinan feels diffs should be "built" Or, Shadowman, he knows too, given that it was one of his customers who supplied a "brand new" Dinan diff for a gear change, so where did all the used gear oil come from...............

Brett Anderson

11-11-2005, 11:11 AM

Wldeyefoto

Re: 3.91

Yes.Grease Monkey

11-10-2005, 09:34 PM

Z8doc

Re: 3.91

Is Dinan going to provide the gears and rebuild the diff for you?

11-10-2005, 04:24 PM

dwz8

Re: 3.91

Acceleration happens quite fast with over 500 hp, driving in first is a necessary evil, second is a quick passthrough, then the fun begins, I agree.
I see of course the difference in usual driving speeds, I take the car up to 150 or 160 mph on a daily basis (if it's not wet), so the 3.64 should work better for me, and I am not living at your altitude.

You are right, you can go back any time if it doesn't work as expected.

Cheers,
Dieter

11-10-2005, 03:51 PM

dwz8

Re: Dreaming of Dragons

Excellent, that answered a couple of my questions. I wish that you will be as happy with your motor as I am with mine.

Thanks,
Dieter

11-10-2005, 02:13 PM

Wldeyefoto

Re: 3.91

Again I appreciate your concerns. What you must keep in mind is that I am losing approximately 17% of my power due to the altitude where I drive. So where your Z8 might become unmanageable with my set-up, I really need all the help I can get. Plus, the change to 3.91 from the current 3.64 is only a 7.5% difference which is really not that radical. For instance, 7000 RPMs in first gear with 3.64 gearing equals 36 MPH and with 3.91 it's 34 MPH. In second gear, I can hit 60 MPH with 3.64 gears at 7000 RPMs and the same speed with 3.91 gears at 7500 RPMs. Cruising in 6th at 3000 RPMs and 3.64 gearing means 79 MPH and I can go just as fast with 3.91 gears with only a 200 RPM increase. Top speed with 7000 RPM limit and 3.64 gearing comes in at 184 MPH whereas 3.91 and 8000 RPMs yields 196. Also, I am not interested in 0-60 contests, where I believe the tires would be the limiting factor anyways, but rather in hard acceleration in the higher gears where I do most of my playing. And, if the higher ratio does prove impractical, I can always go back to 3.64 but my preference is to have too much of a good thing as opposed to not enough! I plan on going to California to drive the car when it is finished because I really want to experience its full potential before I have to resign myself to the effects of high altitude living. Assuming I survive the encounter, I will of course report my findings to all. In the mean time, I want to get back to my dream; it was a very good one!Grease Monkey

11-10-2005, 01:43 PM

Wldeyefoto

Re: Dreaming of Dragons

Thanks for your insightful comments. I am not at liberty to reveal the exact details of how Dinan will achieve the results I described since the techniques are proprietary. In case you aren't aware, Dinan has one of the top "code crackers" in the world on staff. I can tell you that the engine I described already exists and has been thoroughly tested. I have asked Steve to try to go further in my car because of the power loss I must contend with running the car at high altitudes. It remains to be seen just how much more power he can provide.

Steve Dinan did say that the real limiting factor in terms of increasing the redline on the S62 motor is not software related but rather crankshaft related. The firing order BMW uses causes a lot of torsional wrap-up on the crankshaft and extremely high RPM levels would likely result in failure. Fortunately, that level is well beyond 8000 RPMs so it's not an issue in this case.

As far as camshaft design is concerned, you should know that the race S62s Dinan builds were originally designed to turn 8000 RPMs so the cams and the rest of the internal parts are actually optimized for that redline. They restrict them to 6800 RPMs to comply with the class rules which means the engines have a longer life expectancy under race conditions. In other words, they are overbuilt. And, since the primary goal in most race motors is higher horsepower rather than torque, an engine optimized for 8000 RPMs will also be optimized for 6800 RPMs since the horsepower curve is essentially linear in its climb. This is not the case for a torque curve where higher RPMs do not necessarily provide higher output. Ideally, I would like to have more torque than Dinan's motor can provide since torque is what accelerates a car, but a naturally aspirated S62 runs into design limitations which ultimately limit torque output. To overcome those limitations, you need to employ forced induction ala Shadowman's phenomenal Z8 which pumps out somewhere over 550 lb/ft! Since I wanted to stick with a naturally aspirated motor to save weight, but still longed for the scat provided by a torque increase, Dinan recommended going to 3.91 gears which will provide a significant torque multiplication factor and then let the increased RPM limit compensate for the lower speed/RPM in each gear.

I do expect the new motor to be a bit more high strung than my current engine, along the lines of the high revving motors used in modern Ferraris, but since my car is driven strictly for pleasure and not commuting, I don't consider this a drawback.
Grease Monkey

11-10-2005, 03:14 AM

dwz8

3.91

As you might know, I am driving with a 3.64 ratio now. In combination with my engine mods I would most likely not want to go to 3.91.

The acceleration will become so fast that first gear becomes pretty useless. Already now I have quite a challenge to get the power to the ground, unfortunately there are no 345 tires for the Z8...:(
Second gear, slowly rolling, clutch fully engaged, throttle down: wheels start spinning

My experience with acceleration is that it mainly depends on quick shifting and initial grip. 0 to 100 km/h is difficult to measure, as a bit of slip or a non-perfect shift will impact the time considerably at these low 4 sec numbers.
Even 0 to 200 km/h happens in about 12-13 seconds, ending in fourth gear.

With a 3.91 ratio, I would expect serious wheel spin in third also, which makes it difficult to drive on a track. You are always in danger to have a power-oversteer then.

Perhaps it might be a better idea to first to the engine mods, drive with them, and then consider the ratio change?

Again, not critizising, I just want to contribute my experiences with a similarly prepared car.

Cheers,
Dieter

11-09-2005, 04:28 PM

dwz8

Re: Dreaming of Dragons

Congratulations, that sounds like a hot project.

Reading through your posts, I have a couple of questions, based on my own 3 months experience now with 520 little horses...

So you start with a race engine that is laid out for 6,800 revs max. Which should mean that the cams are laid out for max performance at or slightly below this number.
Why do you expect more power by just upping the redline? I would expect completely different cams for an 8,000 revs engine than for a 6,800 revs one?
You mention that the original engine management is to be kept with modifications. There are absolute barriers built into it that are hard to impossible to overcome as far as the redline goes. 8,000 seems to be on the other side, which brings up the question, how will this be done?
My experience of the past months is that the engine management is watching everything that happens, based on the original conditions, and it then uses the modified values to make decisions. Quite easily you get into a situation where it thinks there is a failure - revs too high, differences between cylinders or VANOS, throttle positions etc etc - and it falls into emergency mode. 8,000 appears to be ambitious IMHO. My redline is currently at 7,780 btw.
Given the fact that this is a race engine with all the characteristics of a race engine, I am curious to see how it will be educated to behave like a streetable engine. Typically, a true race engine wouldn't use the normal motor management nor the VANOS, so I can't see a clear way to the engine that you describe.
Please forgive my comments, I wish you all the best in the world with this engine, I am just curious at the technical level.

Cheers,
Dieter

11-09-2005, 02:35 PM

weekendwarrior427

Re: Dreaming of Dragons

Hi Grease Monkey,

Your project really sounds great. I gave up on the Z8 a few years ago simply because in California the engine mods such as you describe are not legal on a street car.

I went the Cobra route. We have a law were 500 Special Constructed Vehicles each year can be totally smog exempt and licensed for the street. Three manufactures now make aluminum FE blocks, which can be built to 600-650 hp specs. I built a KMS Cobra, aluminum body with original dimensions stainless steel frame and all billet aluminum suspension, Wilwood brakes and hydraulics, USA wiring, aluminum differential and I will be going with CV half-shafts. I have a toploader but will be switching to a TKO 600 5 speed. Looking for a 2150 to 2200 lb car.

The car is rude and crude by Z8 standards but I can legally tweak it to my hearts content. Itís not a Cobra, just a replica, so I am not worried about driving it hard.

As a former Cobra Owner, thought you might enjoy. Look forward in reading about you buildup. Z8 is one of the best cars ever built.

11-09-2005, 12:28 AM

shadowman

Re: Dreaming of Dragons

Sir:

Thank you for the "HIGHEST" of compliments........

Your comment brought a wondeful smile.

I remain as stated very excited for you; and I remain confident that the Team @ Dinan will make you smile as well.

Takes care

ShadowmanShadowman

11-09-2005, 12:13 AM

Wldeyefoto

Aw, shucks...

Grease Monkey

11-08-2005, 01:43 PM

Wldeyefoto

Re: Just in time for Michelin PS II

Terrific news! PS2s on the beautiful OE wheels should be an outstanding combination. Thanks for the update.Grease Monkey

11-08-2005, 01:40 PM

Wldeyefoto

Re: Dreaming of Dragons

It was your incredible super-charged S62 project which inspired this dream. You have set the standard and I am just following in your footsteps. Thanks for the encouraging words.Grease Monkey

11-08-2005, 12:32 PM

Wldeyefoto

Re: Any musings from Steve on possible expansions.

Due to the very limited potential for sales, I don't believe Dinan will offer any new Z8 upgrades as a result of this project, but you never know. If there is a possibility of making some of the mods available, I will make sure this board hears about it first. The one thing that may show up would be a more aggressive suspension kit since I have encouraged Steve to play with my car and see if he thinks his "trick" new shocks would make a significant difference. If so, I will try to convince him to engineer a coil-over set-up for the Z8 which would then be available to all. Keep your fingers crossed.Grease Monkey

11-08-2005, 10:19 AM

metzger

Re: Dreaming of Dragons

You're completely insane - I like that in a man.

11-08-2005, 12:25 AM

Z8mania

WOW- that is WILD!

11-07-2005, 11:19 PM

thegunguy

Any musings from Steve on possible expansions...

...to the existing Dinan Z8 product line as a result of the "Dragon" project?

11-07-2005, 09:57 PM

talking of tires anyone hear about the new Pirelli

Run Flats, and are they a good option for our cars?

GM, your 'dragon' sounds like a really awesome project, I hope it will bring you nothing but joy!!

The chat is here;
Z8 images & info

http:www.bmwz8.us

11-07-2005, 07:50 PM

z8.bob

Just in time for Michelin PS II

I have it on good report via SEMA that Michelin will discontinue the PS and PS A/S in favor of going to PS IIs on all sizes. Tires for the Z8 OEM wheels should be available in March 2006.